Why your COVID test results take so long


January 14, 2022 – As the Omicron variant has hit the US, which is now blamed for more than 98% of COVID-19 infections, the demand for laboratory testing has risen sharply – especially as household antigen tests are scarce.

Complaints of respondents who repeat this worrying question are also on the rise:

What takes so long for results?

The promised deadlines of 24 to 48 hours extend to a few days, as people wonder if they should isolate themselves or continue with their regular schedule.

Increased volume is, of course, the main reason, but not the only one.

“You’d be surprised at the time delays,” said Dan Milner, MD, chief medical officer of the American Society of Clinical Pathology, an organization for laboratory experts.

The journey of a nasal swab – from the place of collection to test results arriving via text or email – is more complex and complicated than most people realize, say Milner and other experts. Many steps along the way, as well as staffing and other issues, including the outbreak of COVID-19 among laboratory staff, may delay the processing of results.

First, the issue of volumes

National statistics as well as daily data from individual laboratories reflect an increase in testing requirements.

On January 11, it reached the average for testing at COVID-19 in the United States almost 2 million a day, an increase of 43% over a period of 14 days.

By January 12, Quest Diagnostics, a clinical laboratory with more than 2,000 patient locations in the U.S., had recorded 67.6 million COVID tests since launching the 2020 service. That’s an increase of about 3 million since Dec. 21, when their total number was HRK 64.7 million.

The UCLA Clinical Microbiology Laboratory now handles more than 2,000 COVID tests a day, compared to 700 or 800 a month ago, says Dr. Sc. Omai B. Garner, Director of Clinical Microbiology for the UCLA Health System. And he doesn’t think demand has peaked.

In Tucson, AZ, Paradigm Site Services, which contracts with local governments, businesses and others to provide testing, is doing 4,000 tests a day, compared to a daily number of 1,000 in early November, says Steven Kelly, CEO.

In addition to volume, there are other obstacles that prevent the estimated processing time.

Wiping, retrieval, transportation

“People misunderstand the whole process,” Garner says. One big misconception is that the swab is analyzed right at the site of collection. This is usually not true – with some fast (and expensive) PCR test sites sometimes the exception.

When nasal collection is complete, the sample is sealed in a test tube and then sent to a laboratory. It can be taken by courier service to a local nearby laboratory or it can be sent much further, especially if collected in a rural area.

“Someone could be taken, and the swab has to be out of state,” Garner says.

Even a swab transported by courier service to a local testing lab could take longer than expected if traffic is heavy or the weather gets worse.

Temperature control is important along the way, says Kelly of Paradigm. “Samples must be stored at appropriate temperatures.” Couriers often store samples in refrigerators to transport them.

Arrival at the Lab

Once the swab arrives at the lab, samples must be reported.

Then, how fast it is tested depends on the amount of tests received at the same time – and what the capacity of the laboratory is, taking into account the staff and equipment for sample analysis.

Laboratory staff is another factor. As the demand for tests has grown, it is difficult for laboratories to add enough staff. Requirements vary from state to state, Garner says, but those who analyze the tests must be scientists from clinical laboratories with training and experience. Like other companies, the labs deal with employees who become infected with COVID-19 and have to leave work to isolate themselves.

Potential lab employees also need to cope well in a high-pressure situation, Kelly says. His company has hired another 30 workers in the last 3 weeks, bringing the total to 160. Some work 7 days a week.

Testing equipment – or lack thereof – can also slow down the process.

While Garner says he is often asked if fake testing labs are popping up, he says he is not aware of any. And it’s easy enough to check lab credentials.

Legitimate Laboratories are certified under the CLIA – 1988 Clinical Laboratory Improvement Amendments. According to the CLIA, federal standards apply to all facilities or locations in the United States that test human samples to assess health or diagnose, diagnose, prevent, or treat disease. The CDC has a CLIA Lab Search Tool look for the laboratory by name and check its certification.

States may also provide information on certification and other test details. For example, the California Working Group on Testing COVID-19 publishes its own list of laboratories, with details of locations, number of tests performed per week, and average processing time.

Laboratory analysis

Laboratories are conducting two types of tests to detect COVID-19. Antigen tests detect certain proteins in the virus.

“Laboratory antigen tests aren’t that different” from quick home tests, Milner says. There is a control line and a test line to detect the virus.

PCR (polymerase chain reaction) tests reveal the genetic material of the virus.

“RNA is extracted from the sample and purified through our extraction instrument,” says Mariah Corbit, head of compliance at Paradigm Laboratories.

Special chemicals and enzymes were added. A PCR machine called a thermal cycle performs a series of heating and cooling steps to analyze the sample. PCR technology allows scientists to amplify small amounts of RNA from samples in DNA, which replicates until any virus is detected.

One of the chemicals produces fluorescent light if the virus is in the sample. This signal is detected by a PCR machine.

A PCR test can also give an idea of ​​how many viruses a person has, says Chris Johnson, MD, medical director of Paradigm Site Services.

Once the analysis begins, it is possible to estimate how long the results will take, Milner says.

The longest analysis is for the PCR test, which varies from laboratory to laboratory, but often requires about 1.5 to 2 hours, he says. Antigen analysis “takes a maximum of 20 minutes,” says Milner.

In the case of fast PCR tests, which promise results in 1-2 hours or even less, but can cost $ 300, the processing time can be changed to get results faster, Milner says. And in general, a positive result appears faster than a negative one. “If you read it in real time, you can get a positive result in 20-30 minutes and report it.”

Institutions that offer rapid tests may only do testing on COVID-19 and may process tests in the same place, Milner says, allowing for a faster turnaround. “If they are CLIA certified, the quality of that test should be fine,” he says.

The laboratory definition of processing time for non-rapid tests may differ from the definition of the person waiting for the result. Quest Diagnostics, for example, says its turnaround timeline begins at end of the day on which the sample is collected and ends at end of the day on which the results are reported.

Checking the results

As such, a positive result is reported, as well as a negative one. “There’s no confirmatory testing,” Garner says. “That’s why labs need to run reliable tests.”

But the test is repeated if the original result is not final, says Garner. And if the second time is not final? “We publish it as indefinite,” and another test can be ordered.

After finalization, the results are sent by SMS or e-mail.

Long-term solutions

Since demand is not expected to slow in the near future, long-term solutions are needed.

“From a lab standpoint, we’re all so frustrated that we don’t have the infrastructure and capacity to meet the needs,” Garner says. “In general, we haven’t built the testing infrastructure needed to fight the pandemic.”

At the start of the pandemic, he says, when demand first rose, “we should have seen it as a need to build infrastructure.”

Meanwhile, lab leaders know how important timely results are, but they won’t sacrifice speed for accuracy. “We want to make sure it’s done right,” Kelly says.


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